Age-Related Macular Degeneration
Age-related macular degeneration (AMD) is a disease of the eye that affects more than 10 million Americans and is one of the leading causes of vision impairment and legal blindness. AMD is caused by a deterioration of the retina — the layer of the eye that senses light and relays images through the optic nerve to the brain. The center of the retina is called the macula and is responsible for the detailed central vision that allows people to read, drive and recognize faces. If the macula starts to break down, areas in the center of the visual field begin to look distorted or blurry. Risk factors for AMD include older age, white race and smoking. There is no cure for AMD, but therapies are available that can slow the disease.
Types of Age-Related Macular Degeneration
There are two types of AMD: wet and dry.
Dry AMD affects approximately 90 percent of those with AMD and is associated with small, yellow deposits (drusen) in the macula. Dry AMD causes the macula to lose its function. The most common symptom of dry AMD is blurred central vision that worsens slowly. If dry AMD affects only one eye, symptoms may not be noticeable.
Wet AMD accounts for approximately 10 – 15 percent of all cases of the disease, but it accounts for 90 percent of all severe vision loss from the disease. In wet AMD, abnormal blood vessels beneath the macula start to leak fluid, causing the retina to become distorted. This leakage eventually leads to destruction of the delicate tissue of the macula. Vision loss can occur rapidly. A common symptom of wet AMD is that straight lines appear wavy, and central vision deteriorates.
Treatment of Age-Related Macular Degeneration
Your eye doctor may recommend the daily use of the AREDS supplements, i.e. a special formulation of zinc and antioxidant vitamins (vitamin C, vitamin E and beta carotene), which have been extensively studied in large clinical trials and have been shown to reduce the risk of developing more severe forms of AMD. It should be noted that an increased risk of lung cancer has been noted in some smokers who take high doses of beta carotene. Therefore, it is recommended that AMD patients who are smokers or those with a history of smoking should probably not take beta carotene. Lutein is an antioxidant pigment found in many green leafy vegetables. Extensive research is underway to determine its efficacy in treating AMD. Preliminary results are encouraging and therefore lutein may also be recommended in addition to the AREDS supplements to preserve vision in patients with AMD.
Your eye doctor can provide you with an Amsler grid (a piece of graph paper with thick, dark lines) that you can use to test your vision each day. This grid can be used at home to monitor for the progression of AMD. If the lines appear wavy or distorted, you should see your eye doctor immediately because it may be a sign that your AMD has worsened.
Laser therapy to prevent the blood vessels from leaking is one form of therapy for wet AMD that your eye doctor may recommend. Unfortunately, recurrences after laser treatment are common. A second mode of treatment involves the injection of medication into the eyeball. Macugen (pegaptanib) is an FDA approved medication and has been shown to significantly slow vision loss in patients with the wet form of AMD. Newer medications such as Avastin (bevacizumab) and Lucentis (ranibizumab) are likely to become the treatment of choice for many patients with wet AMD. The injection of theses medications may need to be repeated several times to obtain their full effect however, and it should be emphasized that none of these treatments is likely to improve vision in AMD. They have been shown to slow the progression of vision loss, and further loss of vision may still occur despite these treatments.
A screening eye examination, including detailed examination of the retina, is recommended for all persons 40 years or older, especially those with a family history of eye disease such as AMD. If your eye doctor discovers drusen or other signs of AMD, AREDS supplementation (with or without lutein), an Amsler grid for home monitoring, and frequent eye examinations may be recommended to reduce your risk of developing vision loss from this potentially serious eye condition.